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Tumour grade used in conjunction with other prognostic parameters, such as tumour type, stage and biomarker status, is a critical determinant of patient management in several cancers, especially those that are organ-confined. Pathologists therefore strive for precise grading and there have been ongoing efforts to facilitate grading reproducibility. We explain why this focus on precision may not be necessary in some cases and highlight the critical importance of optimally communicating the histopathological findings in cases where grading is borderline. We also discuss potential issues with the current trend to reduce the number of grading categories in some tumours such as urothelial and endometrial cancers.
Tumour grade is generally a biological continuum with a progressive increase in risk of adverse outcome and no quantum increase in risk at any particular cut-point. Although grade may determine management decisions, individual patients and clinicians may have a different perception of the minimum risk (and hence minimum grade) that would warrant therapy. Hence, the cut-points between grade categories are generally arbitrary. This is analogous to blood pressure and serum prostate-specific antigen (PSA) cut-points used to stratify patients with hypertension and prostate cancer, respectively. For example, PSA cut-points of 10 ng/mL and 20 ng/mL are used to stratify risk for patients with prostate cancer,1 but it is unlikely that there is a significant biological difference between PSA levels of 9 ng/mL (low risk) and 10 ng/mL (intermediate risk).
Grade is also a morphological continuum with arbitrary and subjective cut-points, such as the 5% and 50% solid component in endometrial carcinoma.2 Hence, there is an inevitable grey zone around the borders of each grade category that is associated with significant intraobserver and interobserver reporting variability. Several studies have shown only limited reproducibility in the reporting of tumour grade in many cancers.3 4 However, it should be recognised that …
Handling editor Yoh Zen.
Twitter @MuraliV72899596, @runjanchetty
Contributors The first draft was written by MV. All authors contributed to the writing of the final version.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Commissioned; internally peer reviewed.